Arcing grid case support means



Jan. 14, w w CAMP 3,422,235

ARCING GRID CASE SUPPORT MEANS Filed Jan. 28, 1966 Sheet of 5 L 97 I Mg 5 1f? 783 M rwrae mm ,7 H5 I: 15,; Q WW/M141 1 n4 om,

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w. w. CAMP Jan. 14, 1969 ARCING GRID CASE SUPPORT MEANS Sheet Filed Jan. 28 1966 Jan. 14, 1969 w.w. CAMP ARCING GRID CASE SUPPORT MEANS Filed Jan. 23, 1966 Sheet 3 of M VEIVTGA.

W/LL/AM W (AM/ United States Patent Ofiice 3,422,235 Patented Jan. 14, 1969 18 Claims This invention relates to electric circuit breakers and more particularly to a support arrangement for the magnetizable grids which control the arcs that tend to arise between the circuit breaker contacts upon separation of the contacts.

It is an object of this invention to form the insulating case of the circuit breaker so that the grids are supported directly by the case in a compact arrangement which not only supports the grids but provides multiple,'obstructed vent openings and longitudinal passages on the sides of the grids.

Another object of this invention is to provide a support arrangement for the conductor which carries the stationary contact similar to the arrangement provided for the grids.

I The support for the grids and the conductor to which the stationary contact is secured is provided by two halfc ases which have two similar, but opposed, support walls forming two supports for each grid and the conductor, and opposed, mating but dissimilar wall portions forming the third support for each grid and the conductor.

The vent openings are formed in abutting peripheral walls of the two half cases and comprise lateral, upper and lower, vent openings and an intermediate, longitudinal vent opening. Insertion of any member into the case through the vent openings is restricted because the lower opening is blocked by the conductor to which the stationary contact is secured, the longitudinal vent opening is obstructed by its own zig-zag shape, and the upper opening is blocked by interior wall portions of the halfcases.

The foregoing and other objects of the invention, the principles of the invention, and the best mode in which I have contemplated applying such principles will more fully appear from the following description and accompanying drawings in illustration thereof.

In the drawings,

FIG. 1 is a side elevation view of a circiut breaker embodying the invention, one of the half-cases of the circuit breaker being removed to show the internal part-s of the circuit breaker, the contacts being shown in the open position;

FIG. 2 is a side elevation view looking at the interior of the half-case not shown in FIG. 1 and showing only the half-case;

FIG. 3 is a view of the right-hand end of the circuit breaker illustrated in FIG. 1, but after the two half-cases have been assembled together;

FIG. 4 is a partial, sectional view taken along the line 4-4 in FIG. 1 and showing a top view of one of the magnetizable grids and a part of the support conductor for the stationary contact;

FIG. 5 is a partial, sectional view taken along the line 55 in FIG. 1 and showing a top view of the stationary contact and its support conductor;

FIG. 6 is a partial perspective view of the right hand portion of the half-case shown in FIG. 1;

FIG. 7 is a partial, perspective view 'of the left hand portion of the half-case shown in FIG. 2;

FIG. 8 is a sectional view taken along the line 8-8 in FIG. 1, but illustrating the mechanism in end elevation, and after assembly of the circuit breaker; and

FIGS. 9 and 10 are side elevation views of the terminals only and shown prior to assembly as part of the circuit breaker.

Referring to the drawings, the circuit breaker 10 comprises an insulating case 12, preferably molded from a plastic material, divided into two juxtaposed, approximately half-cases 14 and 16. The circuit breaker 10 includes a mechanism 18 which is mounted within and enclosed by the case 12, but for a part of a handle 19 which extends out of the case 12, as shown. The mechanism 18 comprises a movable contact 20 carried by a movable arm 21 and engageable with a stationary contact 22, the latter being carried by a support conductor 23 forming part of a terminal 24. The movable arm 21 is connected by a flexible conductor 26 to one end of a coil 30 forming part of an electromagnetic device 32 which is also enclosed by the case 12 and which is associated with the mechanism 18 to trip open the contacts on predetermined overloads. The electrical circuit of the circuit breaker is completed by connecting the other end of the coil 30 to a terminal 36. As shown, the terminals 24 and 36 are carried by the case 12 and extend outwardly therefrom.

Further, the movable arm 21 is biased by a spring 38 toward the open position of the contacts 20 and 22 and the movable arm 21 is mounted on a pin 39 about which it pivots, the pin 39 having end portions 33 carried by two spaced plates 34 and 35 (FIGS. 1 and 8) forming a frame 40, only the plate 34 being shown in FIG. 1. The movable arm 21 is also connected by a pin 42 to a toggle or latching mechanism 44, the latter being in turn connected to the handle 19 by a pin 45. The handle 19 pivots about a pin 46 having end portions 47 also carried by the spaced plates 34 and 35.

The frame plates 3 and 35 are integral with an L- shaped magnetic frame 41 forming part of the electromagnetic device 32 and to which is secured a time delay tube 43 housing a spring biased magnetizable core (not illustrated) movable against the retarding action of a suitable fluid to provide a time delay before tripping of the mechanism at certain overloads. As illustrated, the frame 41 also carries the coil 30.

The operation of this type of mechanism 18 and electromagnetic device 32 is generally set forth in Pat. No. 2,360,922, among others, but for claritys sake may be briefly described as follows-when the handle 19 is rotated clockwise, as viewed in FIG. 1, the toggle mechanism 44 and the movable arm 21 all move down, against the bias of the spring 38, and move the contact 20 into engagement'with the contact 22, the contacts assuming the closed position, not illustrated.

Upon the occurrence of a predetermined overload condition, assuming the circuit breaker to be in the contacts closed position, not illustrated, the armature 50 (which is also part of the electromagnetic device 32) is attracted toward the pole piece 52 either after a time delay period or virtually instantaneously, depending on the overload current. The armature 50 pivots toward the pole piece 52, about a pin 54 whose end portions are also carried by the spaced frame plates 34 and 35 and which carries the armature 50, causing the oppositely extending trip member 56 (which'is integral with the armature 50) to pivot to the right and to trip the arm 58 forming part of a latch 60 which, when the toggle mechanism 44 has been moved to the contacts closed position, is juxtaposed with the trip member 56, whereupon the toggle mechanism 44 collapsesunder the pressure of the opening-spring 38.

To minimize and/or extinguish the arcs, that may form between the contacts 20 and 22 whenever the contacts are opened, assuming the circuit breaker to be energized, this invention provides a stacked array of three magnetizable, metal grids 70, 71 and 72 supported by 3 the two half-cases 14 and 16, as shown in FIGS. 1 and 4, within the case 12, and above the support conductor 23 and the stationary contact 22.

The half-cases 14 and 16 comprise, respectively, side walls 80 and 81 and peripheral, marginal upper walls 82 and 83, bottom walls 84 and 85, end walls 86 and 87 (facing the grids 70, 71 and 72) and end walls 88 and 89 (facing the coil 30) extending therefrom and abutting each other to define a cavity 90 within which is placed the mechanism 18 and the electromagnetic device 32. The side walls 80 and 81, however, have inwardly projecting walls 94 and 95, respectively, which separate the cavity 90 into a main cavity 96 and an arcing chamber 97.

Referring to FIGS. 1 and 4, all of the grids 70, 71 and 72 are of the same size and shape, but referring only to grid 70 for brevity, the grid 70 has generally a U-shape with a central, rear integral lug 100. Similarly, all of the grids 70, 71 and 72 are supported by the half-cases 14 and 16 in a similar arrangement, but referring only to the grid 70 for brevity, the end portions 101 and 102 of its legs are received in side slots 103 and 104 respectively, formed in the walls 94 and 95. The rear lug 100 is received in a rear slot 105 formed in the wall 86.

As illustrated in FIGS. 4, 6 and 7, the side slots 103 and 104 are completely open on two contiguous sides, i.e., they are open facing each other and also open on the side facing the rear slot 105. The rear slot 105 is completely open, in so far as the half-case 14 is concerned, on two contiguous sides one of which faces the side slots 103 and 104, but only partially open on the third side, as shown. As shown in FIG. 4, the slot 105 is closed on one side by a portion of the surface 109 forming part of half-case 16.

The side slots 103 and 104 further comprise opposed surfaces 110 and the rear slot 105 comprises opposed surfaces 111. Note that (as shown in FIG. 4) the opposed surfaces 111 of the rear slot 105 do not extend the width of the slot 105 but instead fall short of the surface 109.

As shown in FIG. 4, the legs and base of the U-shaped grid 70 are spaced from the adjacent surface of the halfcases 14 and 16 to define longitudinal passages around three sides of the grid 70, the longitudinal passage 120 being formed around one leg and about one-half of the base of the grid 70 in the half-case 14 and the longitudinal passage 121 being formed around the other leg and about one-half of the base of the grid 70 in the halfcase 16.

The distance between the opposed upper and lower surfaces 110 or 111 is made such, relative to the thickness of the grid, that the grid is received by the slots 103, 104 and 105 with a sliding fit. Preferably, some peripheral clearance is provide-d with the edge surfaces of the' grid, as shown in FIG. 4, to accommodate manufacturing tolerances and any lateral expansion of the grid which may take place relative to the half-cases. Also, as shown, the grid 70 is of uniform thickness, including the rear lug, which is integral therewith and of the same thickness as the remainder of the grid.

The conductor 23 is supported by the half-cases 14 and 16 by an arrangement similar to that of the grids 70, 71 and 72. As shown in FIG. 5, the conductor 23 has integral, side lugs 130 and 131 (of the same thickness as the remainder of the conductor) which extend into and are supported in slots 132 and 133. The slots 132 and 133 are open only at the front because the walls 94 and 95 are extended toward the end walls 86 and 87, as shown in FIGS. 5, 6 and 7, but the walls 94 and 95 fall short of the end walls 86 and 87 to provide a larger lateral dimension to the chamber 150 formed below the conductor 23.

The conductor 23 has an integral rear lug 138 (of the same thickness as the remainder of the conductor) which is received in a rear slot 139 formed in the walls 86 and 87, the rear slot 139 having substantially the same shape and form as the rear slot for the grid 70.

The distance between the opposed upper and lower surfaces of the slots 132, 133 and 139 (FIGS. 6 and 7) is made such, relative to the thickness of the lugs 130, 131 and 138 (FIG. 5) that the lugs are received by the slots with a sliding fit. Also, some peripheral clearance is provided by the slots 132, 133 and 139 around the lugs 130, 131 and 138 to accommodate manufacturing tolerances and any lateral expansion of the conductor 23 which may take place relative to the halfcases.

It is seen that the conductor 23 has edge portions, FIG. 5, between the lugs 130, 131 and 138 which ,are spaced from the adjacent surfaces of the half-cases 14 and 16 to form a continuation of the longitudinal passages and 121.

Further, while the conductor 23, as shown in FIGS. 4 and 5, is wider than the diameter of the stationary contact 22 which is secured to it and sits upon it, and is raised above the upper surface of the conductor 23, as shown in FIG. 1, the width of the conductor 23 is small enough to define with the inner leg surfaces of the grid 70 longitudinal passages 146 and 147.

The terminal 24 is bent upon itself, as shown in FIG. 1, and comprises the conductor 23, and integral vertical and horizontal parts 140 and 141, respectively. The horizontal part 141 overlies surfaces 142 (FIGS. 6 and 7) and the vertical part 140 extends through a vertical slot 143 and has side lugs 145 (FIG. 10) which engage the case and help restrain upward movement of the terminal 24. As shown, the conductor 23 and the horizontal part 141 generally define a V-shape.

Thus, it is seen that a generally triangular chamber is provided below the conductor 23 which, when viewed as in FIGS. 1, 6 and 7 is defined generally by the lower surfaces of the conductor 23, the case surfaces 142, 151 and 152, the lower, inner surfaces of the walls 86 and 87, the lower surfaces of the enlarged parts of the opposed walls 94 and 95, and the lower, inner surfaces of the side walls 80 and 81 between the opposed walls 94, 95 and the end walls 86, 87. Communicating with the triangular chamber 150 is a lateral, lower vent opening formed in the end walls 86 and 87, approximately half of the opening 160 being formed in each end wall.

As shown in FIG. 3, a vertical, longitudinal vent opening 161 is provided, by spacing from each other the opposed surfaces 162 and 163 of the walls 86 and 87. The surfaces 162 and 163, when viewed as in FIGS. 4 and 5, have approximately a Z-shape and form a zig-zag vent opening. The surface 163 is formed, as viewed in FIGS. 4 and 5, by horizontal portions 109 and 166 and an inclined surface 165 connecting the two. The surface 162 is formed by a horizontal portion 174, and inclined portion 173, the two being connected by inclined surface 175. Note that the part of the vent 161 opening to the inside of the case diverges inwardly to provide a larger opening on the inside which decreases in width as the opening progresses toward the outside, as shown in FIG. 4, to facilitate entry into the opening of the arc gases. The surface 165 extends vertically a distance greater than the space between entry surfaces 166 and 174, whereby insertion of an object into the interior of the circuit breaker will be obstructed by the surface 165.

The vent opening 161 communicates with the arcing chamber both above and below the plane of contact of the movable and stationary contacts and intersects such plane. The vent opening 161 communicates with the rear slots 105 and 139, as shown in FIGS. 4 and 5, and, also, the vent opening 161 communicates with the lower vent opening 160, as shown in FIG. 3.

Further, portions of the vent opening 161 are disposed between the rear lugs 100 and 138 of adjacent grids 70,

71 and 72 and of the conductor 23 to provide a direct vent opening to the space between the grids or the lowest grid 70 and the conductor 23.

The vent opening 162 is terminated at the top by a key projection 168, FIGS. 3 and 7, formed on the end wall 87 and received by a suitable mating space in the end wall 86.

The arcing chamber 97 is also vented at the top through an upper, lateral vent Opening 170 which curves downwardly at approximately a right angle so that entry of any member into the circuit breaker case through the opening 170 will tend to be obstructed by the surfaces 171 depending, abutting walls 172.

As shown in FIGS. 4, 5 and 7, the entry portions of the slots 104 and 133 are well rounded so as to facilitate placement of the half-case 16 upon the grids 70, 71 and 72 and the conductor 23, after all the various parts have been positioned as shown in FIG. 1 within the half-case 14.

The terminal 36 is received within 5. slot 180' (FIGS. 1 and 2) formed by the two half-cases, and the terminal 36 has spaced notches 181 (FIG. 9) receiving spaced nibs 182 (FIG. 2) at opposite ends of the slot 180 to restrain vertical (as viewed in FIG. 1) movement of the terminal 36. The terminal 36 is provided with an integral upper portion 183 to which is soldered one end of the coil 30.

Referring to FIG. 8, it is seen that the end portions 33 and 47 of the pins 39 and 46, respectively, which extend out beyond the frame plates 34 and 35, are received and supported in openings 183 and 184 (FIG. 2) in raised bosses 185 and 186, respectively, the latter extending inwardly from the side walls 80 and 81. The frame plates 34 and 35 abut against the opposed faces of the bosses 185 and 186 and space the mechanism 18 and the electromagnetic device 32 from the side walls 80 and 81.

Thus, by properly aligning the openings 183 and 184 and the slot 132 in the half-case 14 and by properly aligning the openings 183 and 184 and the slot 133 in the half-ease 16 (FIG. 2) the mechanism 18 and movable contact 20 have been properly aligned relative to the stationary contact 22.

Since it is preferred to use a rear lug 138 at the rear of the conductor 23, to help resist the contact closing force and minimize bending of the conductor 23 during closing of the contacts, it is seen that the rear slot 139 must also be properly aligned relative to the slots 132 and 133 for the stationary contact 22 to be properly aligned relative to the movable contact 20.

Thus, the electromagnetic device 32 and the mechanism may be completely assembled outside the case, including the terminal 36 which is soldered to the coil 30, and the various parts may then be placed as one sub-assembly upon the half-case 14, after the grids 70, 71 and 72, the terminal 24 have been placed in the half-case 14. Insert rivets 200 (FIG. 1) are placed within suitable openings in the half-case 14 and thereafter, the half-case 16 may he slipped over the various parts. To complete the assembly of the circuit breaker, bottom rivets 201 (FIG. 3) are added and then the rivets 200 and 201 are peened.

As viewed in FIG. 4, the side slots 103, one preferably made with sufficient depth and width clearance so that upon initial insertion of the grids into the slots 103 and the rear slots 105, the grids take a slightly inclined or cocked position if inserted fully into the slots 103, the rear lug 100 being cocked slightly, downwardly, as viewed in FIG. 4. The thickness of the grids is preferably such as to be received snugly into the slots 100' and 103. Also, the opposite walls 110 of the slots 104 are tapered at the entry portion of the slots 104 to diverge outwardly (see FIG. 7) to facilitate placement of the half-case 16 upon the grids after the grids have been placed in the halfcase 14. vWhen the half-case 16 is placed upon the grids, the surface 109 engages the rear lugs 100 and cams the grids to the position shown in FIG. 4, i.e., centrally aligned with the contact 22, so that the grid leg end portions 101 and 102 assume the central position shown in FIG. 4.

The thickness of the conductor 23 relative to the longer opposed walls of the side slot 132 and to the opposed walls of the rear slot 139 is also preferably such that the lugs 130 and 138 are received snugly in the slots 132 and 139. Also, the longer opposed walls of the side slot 133- are tapered to diverge outwardly (see FIG. 7) to facilitate placement of the half-case 16 upon the conductor 23 after the conductor has been placed in the half-case 14.

It will be noted that the grids 70, 71 and 72 have a symmetrical shape about a longitudinal, horizontal axis passing through the centers of the stationary contact 22, as viewed in FIG. 4, and the movable contact 20. The rear lug extends backwardly into the longitudinal, vertical vent opening 161 at the middle of the base of the grids, i.e., the rear lugs forming a central, extension of the grid bases, guiding the arc and are gases into the vent 161. Thus, the lugs 100 and the inner part of the vent 161, i.e., the horizontal surface 109 and the inclined surface 173, are placed in the path of movement of the arc and of the arc gases, since with such grids the are tends to move toward the base and center thereof.

Further, the ends of the legs of the grids are received fully within the slots, as shown in FIG. 4. Also, the lugs and 131, as shown in FIG. 5, are completely surrounded on three sides by portions of the walls 94 and 95. Thus, the sharp edges or points of the grid legs and the lugs 130 and 131 are not exposed to the arc and, since it is shown that an arc tends to jump to a point, this tends to reduce the jumping of the arc to the grids or to the conductor 23. When an arc jumps to the grids it may cause a metal bridge to form between grids which would magnetically short the bridged grids, an undesirable result.

Referring to FIGS. 1, 2 and 8, the pin 46 about which the handle 19 pivots has a cylindrical shape and its end portions 47 are received in accurately positioned circular holes 184 having a close, accurate but slidable fit with the pin 46. The pin 39 about which the movable arm 21 pivots is also of cylindrical shape but its end portions are received in slightly elongated, accurately located holes 183, FIG. 2, the horizontal tolerance on these holes being controlled closely for an accurate fit. Thus, proper location of the circular hole 184 fixes the position of the electromagnetic device 32 and of the linkage mechanism 18 both with respect to a vertical and a horizontal axis through the center of this hole. However, the hole 183 permits the electromagnetic device 32 and the linkage mechanism 18 to move vertically up and down, as viewed in FIGS. 1 and 2, this movement taking place slightly upon closing of the contacts. Note that proper alignment of the holes 183 and 184 with respect to the slot 133 in the half-case 16, and the proper alignment of the holes 183 and 184 with respect to the slots 132 and 139 in the half-case 14, is all that is required to properly align the electromagnetic device 32 and the linkage mechanism 18 relative to the stationary contact 22.

As the circular hole 184 wears and tends to elongate, the frame plates 34 and 35 are provided with semi-circular marginal portions 220 and substantially horizontal portions 222 on opposite sides thereof, one or the other or all of which, engage correspondingly shaped abutments 224 and 226 (FIG. 2) formed on the half-cases.

Note that the frame plates 34 and 35 are continuous, flat plates and have holes which carry the handle pin 46, the armature pin 54 and the movable arm pin 39. These holes are punched in the flat plate from which the integral magnetic frame 41 and side plates 34 and 35 are formed and then the plate is bent to the shape of the frame 41 and of the frame plates 34 and 35 shown, but no bends intervene between the holes for the pins 39, 46 and 54, so that the positions of the holes relative to each other remains as when initially punched.

Since the lugs 130, 131 and 138 (which are integral with the conductor 23) are extensions of the surface which directly carries the stationary contact 22, no bend or other discontinuity intervenes between the part of the conductor 23 which carries the contact 22 and the support lugs 130, 131 and 138, so that once the slots for these lugs have been positioned accurately relative to the holes 183 and 184, the plane of engagement of the contacts is accurately established.

Having described the invention, I claim:

1. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, said case being divided into two approximate half-cases, each half-case being formed by a side wall and integral peripheral walls, a conductor within said case carrying said stationary contact, a plurality of magnetizable grids stacked above said stationary contact, each grid having two legs and a base, said halfcases having first and second opposed walls defining side slots completely open on two contiguous sides to receive and support portions of said legs, one of the half-cases having a third wall defining rear slots completely open on two contiguous sides, one of which faces the side slots, and partially closed on a third side, to receive and support a portion of said base, and the other half-case having a fourth wall overlying said third wall to restrain movement of said grids out of the rear slots.

2. The structure recited in claim 1 wherein said third and fourth walls also define a longitudinal vent opening communicating with said rear slots and the interior of said case.

3. The structure recited in claim 1 wherein the grids have substantially a U-shape, the first and third walls are formed on one half-case and the second and fourth walls are formed on the other half-case, said first and second walls projecting inwardly from the side walls of the halfcases and the third and fourth walls being spaced from the base of the Ushaped grids so as to define longitudinal gas passages on three sides of said grids, said half-cases also having vent openings in communication with opposite ends of said passages.

4. The structure recited in claim 3 wherein said third and fourth walls also define a longitudinal vent opening communicating with said rear slots and the interior of said case, said longitudinal vent opening having approximately a Z-shape in cross-section so as to obstruct access through said longitudinal vent opening from the outside of said case into the interior thereof.

5. The structure recited in claim 4 wherein said vent openings in communication with opposite ends of said passages are formed one at the upper end and one at the lower end of said passages, the upper vent opening is obstructed by blocking portions of said half-cases, and the lower vent opening is obstructed by said support conductor.

6. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, a conductor within said case including a stationary contact, a plurality of magnetizable grids stacked above said stationary contact, the closest grid to said conductor and stationary contact being spaced above said stationary contact to define lateral passages, said conductor being spaced from said case to define first longitudinal passages, said conductor and said case defining a chamber below said conductor, said grids having substantially a U-shape, the legs of the U-shape of the grid closest to the stationary contact being laterally spaced, in part, from the edge portions of said conductor closest thereto to define second longitudinal passages on opposite sides of the stationary contact, said stationary contact being smaller in width than said conductor and defining a plane of engagement with said movable contact above the surface of said conductor, whereby upon initial separation of the contacts, are gases generated at such time flow laterally and longitudinally.

7. The structure set forth in claim 6 wherein said case forms a longitudinal vent opening intersecting the plane of engagement of the stationary and movable contacts and communicating with the interior of said case.

8. The structure recited in claim 7 wherein said case forms a lateral vent opening communicating with said chamber.

9. The structure recited in claim 8 wherein said longitudinal vent opening has a zig-zag shape to obstruct access into the interior of said case, and access into the interior of said case through said lateral vent opening being obstructed by said conductor.

10. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, an electromagnetic device for tripping said mechanism on predetermined overloads, said case being divided into two half-cases, each half-case being formed by a side wall and integral peripheral walls, a conductor within said case carrying a stationary contact, said electromagnetic device including two spaced frame plates supporting said mechanism, said mechanism including two pins supported by said frame plates and having end portions extending beyond said frame plates, each half-case having two raised bosses forming two openings receiving and supporting the two pin end portions, said conductor forming part of a first terminal, said electromagnetic device including a coil, a second terminal to which an end portion of said coil is soldered prior to placement of said electromagnetic device and said mechanism upon one of said half-cases, said conductor having two lugs, said half-cases having first and second walls defining two opposed side slots to receive and support said lugs, whereby said mechanism, said electromagnetic device and said first terminal, on the other hand, are positioned relative to each other, as to each half-case, by virtue of the two openings and the one side slot, of each half-case.

11. The structure recited in claim 10 wherein said conductor includes a rear lug, one of the two half-cases having a third'wall defining a rear slot completely open on two contiguous sides, one of which faces said side slot, to receive and support said rear lug, and the other of said half-cases having a fourth wall juxtaposed to said second wall to restrain movement of said rear lug out of the rear slot.

12. The structure recited in claim 2 wherein said grids have a symmetrical shape about an axis through the center of said stationary contact, said longitudinal vent opening communicates with the bases of the grids at the centers of the bases, said bases extending partly in said longitudinal vent opening, whereby said longitudinal vent opening is aligned, at least in part, with the direction of movement of the arc.

13. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, said case being divided into two approximate half-cases, each half-case being formed by a side wall and integral peripheral walls, a conductor within said case carrying said stationary contact, a plurality of magnetizable grids stacked above said stationary contact, each grid 'having two side legs and a base said halfcases having first and second opposed walls defining side slots to receive and support said side legs, one of the halfcases having a third wall defining rear slots to receive and support portions of said bases and the other half-case having a fourth wall overylying said third wall, the thickness of said grids being such that they are received snugly by the half-case having both side and rear slots, the side slot in the half-case having side slots but no rear slots being tapered to diverge outwardly so as to facilitate placement of the half-case with only the side slots upon grids.

14. The structure recited in claim 13 and further including a conductor carrying said stationary contact, the plane of the conductor carrying the stationary contact ineluding side and rear support portions, the thickness of said support portions being such that they are received snugly by the half-case having both side and rear slot, the side slots in the half-case having side slots but no rear slots being tapered to diverge outwardly so as to facilitate placement of the half-case with only the side slots upon said grids.

15. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, an electromagnetic device for tripping said mechanism on predetermined overloads, said case being divided into two approximate half-cases, each half-case being formed by a side wall and integral peripheral walls, a conductor within said case carrying a stationary contact, said electromagnetic device including two spaced frame plates supporting said mechanism, said mechanism including two pins supported in holes in said frame plates and having end portions extending beyond said frame plates, each half-case having two openings receiving and supporting the two pin end portions, said conductor being part of a first terminal, said electromagnetic device including a coil, a second terminal to which an end portion of said coil is connected prior to placement of said electromagnetic device and said mechanism upon one of said half-cases, the part of said conductor carrying said stationary contact having two support portions on opposite sides, said half-cases having first and second walls defining two opposed side slots to receive said support portions, said stationary contact being carried intermediate said support portions with substantially no bending of the conductor between the place where the stationary contact is carried by the conductor and the support portions, whereby said mechanism, said electromagnetic device and said first terminal, on the other hand, are positioned relative to each other, as to each half-case, by virtue of the two openings and the one side slot, of each half-case.

16. The structure recited in claim 15 wherein the frame plates have holes supporting a pin carrying an armature of said electromagnetic device, each frame plate is one continuous flat piece with no intervening bends between said holes in said frame plates for said pins.

17. In a circuit breaker, the combination of an insulating case, stationary and movable contacts within said case, a mechanism for moving said movable contact away from said stationary contact, an electromagnetic device for tripping said mechanism on predetermined overloads, said case being divided into two approximate half-cases, each half-case being formed by a side wall and integral peripheral walls, a conductor within said case carrying a stationary contact, said electromagnetic device including two spaced frame plates supporting said mechanism, said mechanism including two pins supported in holes in said frame plates and having end portions extending beyond said frame plates, each half-case having two openings receiving and supporting the two pin end portions, said conductor being part of a first terminal, said electromagnetic device including a coil, a second terminal to which an end portion of said coil is connected prior to placement of said electromagnetic device and said mechanism upon one of said half-cases, one of said pins being the pin about which the handle pivots, the other pin being the pin about which the movable arm pivots, the hole for the handle pin being circular and closely receiving said handle pin, the hole for the movable arm pin being slightly elongated, said frame plates having marginal surfaces, said half-cases having abutments engageable by said frame plate marginal surfaces, so that as the circular hole wears and elongates movement of the frame plates is limited, during closing of the contacts, by the abutments.

18. The structure recited in claim 1 wherein said side slots receive the end portions of said legs within said first and second opposed walls leaving no ends of said legs outside of said first and second walls.

References Cited UNITED STATES PATENTS 2,363,606 11/1944 Maseng 200-144 2,429,722 10/1947 Jennings 200--144 X 2,647,191 7/1953 Humpage 200168 2,719,203 9/ 1955 Gelzheiser et al 200-144 ROBERT S. MACON, Primary Examiner.

US. Cl. X.R. 

1. IN A CIRCUIT BREAKER, THE COMBINATION OF AN INSULATING CASE, STATIONARY AND MOVABLE CONTACTS WITHIN SAID CASE, A MECHANISM FOR MOVING SAID MOVABLE CONTACT AWAY FROM SAID STATIONARY CONTACT, SAID CASE BEING DIVIDED INTO TWO APPROXIMATE HALF-CASE, EACH HALF-CASE BEING FORMED BY A SIDE WALL AND INTEGRAL PERIPHERAL WALLS, A CONDUCTOR WITHIN SAID CASE CARRYING SAID STATIONARY CONTACT, A PLURALITY OF MAGNETIZABLE GRIDS STACKED ABOVE SAID STATIONARY CONTACT, EACH GRID HAVING TWO LEGS AND A BASE, SAID HALFCASES HAVING FIRST AND SECOND OPPOSED WALLS DEFINING SIDE 